Control apparatus



United States Patent 1111 3,548,794

[72] Inventor Jeffrey M. Lazar [56] References Cited Dakota, Minn.UNITED STATES PATENTS 1 PP 792,637 2,447,261 8/1948 Mock 123/119 1 141,1969 2,882,880 4/1959 Reggio 123/1403 1 Famed DQ221197 3,169,5132/1965 l-lennequin" 123/1403 [73] AS51811 3,388,898 6/1968 Wyczalek....123/119x Mil'mlwlismnn- 3,392,714 7/1968 Braun m1. 123/119 a corporationof Delaware Primary Examiner-Laurence M. Goodndge Attorneys-Charles JUngemach, Ronald R. Reiling and 154 CONTROL APPARATUS 10 Claims, 1Drawing Fig. [52] (1,5,0! 123/119, ABSTRACT: A fluidic fuel controlsystem wherein parame- 123/139, 123/140; 261/159 ters includingvolumetric flow rate and temperature of air en- [51] I t, F02 17/02tering a mixing chamber are sensed and signals indicative [50] FieldofSearch 123/1 19, thereof m l ip i to pr vide a signal for controllingfuel flow into the mixing chamber.

No: 102" A57 as c 13 PATENTEUDECZZISYG 354 7 INVENTOR. JEFFREY M. LAZARM/ ATTORNE/ CONTROL APPARATUS BACKGROUND OF THE INVENTION This inventionpertains generally to fuel control systems and more particularly tofluidic fuel control systems whereinfuel flow into a mixing chamber iscontrolled in response to mass air flow thereinto.

The operationof an .internal combustion engine requires that the air andfuel be mixed in certain proportions before being supplied to thecombustion chamber or chambers of the engine. In a reciprocating engine,the fuel to air ration is normally controlled by means of a conventionalcarburetion system. This carburetion system basically comprises a mixingchamber and means for allowing-the entry of fuel and air thereinto. Thefuel-air mixture from 'the mixing chamber is supplied to the cylinder orcylinders of the engine by means of an intake manifold. A throttle valveis located between the mixing chamber and the manifold. Variousauxiliary devices may be provided for controlling the starting fuelmixture and for controlling the fuel mixture under transient operatingconditions.

In normal operation, both fuel and air are drawn into the mixing chamberby meansof a partial vacuum which is transmitted thereinto from theintake manifold. A conventional carburetor controls primarily thevolumetric fuel and air flows into the mixing chamber, whereas a properfuel to air mixture requires control of the fuel and air mass flows intothe mixing chamber. Since a conventional carburetordoes not compensatefor air temperature or air pressure, it cannot provide an optimum fuelto air mixture under many operating conditions.

The use of an improper fuel-air mixture in an internal combustion engineresults in a number of detrimental effects. One of these is that optimumengine operation and efficiency cannot be achieved. Another is thatnoxious exhaust gases including excessive unburned combustion productsare produced.

A further disadvantage of most conventional carburetors is that theycontain a number of intricate moving mechanical parts includingbutterfly and needle valves, fuel floats, mechanical temperature sensorsand complicated interconnecting linkages. The fact that all of theseparts must be manufactured and assembled increases the cost andcomplexity of production. In addition, the working interrelationships ofthese mechanical parts is critical. Accordingly, the initial adjustmentsmust be carefully performed. Further, since moving mechanical parts areincluded, they are subject to wear and the carburetor must beperiodically readjusted.

Various of these problems have been at least partially overcome byfluidic fuel control systems in whicltat least certain of the parametersnecessary to compute mass air flow into the mixing chamber are sensedfluidically. Further, in these system, the fuel control signal isgenerally produced from computations which are carried out by means offluidic elements. However, the only fluidic computation which hasheretofore been utilized in these systems has been summation. Since airmass flow rate is given by the expression pV/Rt, where p is the airpressure, V is the volumetric flow rate, R is a constant and t is airtemperature, it can be seen that a summation can give only anapproximation to the'air mass flow rate function. Further, thisapproximation is only good over limited ranges of values of the variousparameters. It can also be seen that a fuel control system must includemeans for multiplying the various parameters necessary to computeair'mass flow rate in order to produce a true air mass flow rate signal.Such a signal is required if a proper fuel to air mixture is to beprovided.

Since prior art carburetion systems do not provide for multiplyingsignals indicative of any of the sensed parameters, they cannot providean optimum fuel to air mixture for all operating conditions. Thus, it isapparent that these systems are not generally satisfactory for. use withmodern internal combustion engines.

SUMMARY OF THE INVENTION The applicant's fuel control system comprises amixing chamber in combination with an air intake passage and a fuelnozzle. Means is provided for sensing at least volumetric flow rate andtemperature of the air entering the mixing chamber through theair'intake passage. Signals indicative of the volumetric air flow rateand air temperature are multiplied to generate a signal indicative ofmass air flow into the mixing chamber. This signal is supplied to afuel-metering valve which controls the flow of fuel into themixingchamber through the fuel nozzle. Means may also be provided forcompensating for variations in air pressure. Additional means may beprovided for sensing engine acceleration and loading and for sensingengine temperature. Signals indicative of the two last named parametersare utilized to improve transient engine operation.

In accordance with the teachings of this invention, the ap plicantsunique fluidic fuel control system provides accurate control over thefuel to air mixture supplied to the engine, thus improving engineefficiency and decreasing unburned combustion products in the engineexhaust gases Automatic compensation is provided for variations in thevolumetric air flow into the mixing chamber due to such factors asclogging of an aircleaner in the air intake passage. In addition, theapplicants invention makes maximum use of fluidic components in whichthere are no moving parts. Accordingly, wear is minimized and maximumreliability is achieved.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTIn. the figure, reference numeral 10 generally designates fuel-airsupply apparatus for a reciprocating internal combustion engine.Apparatus 10 includes fuel-mixing apparatus 11 which supplies a fuelmixture to an intake manifold 12. Fuel-mixing apparatus 11 is muchsimplified from a conventional carburetor in that it includespractically no moving parts or accessory devices. Fuel-mixing apparatus11 is mounted on manifold 12 by means of a plurality of bolts 13.Manifold l2 distributes the fuel mixture to the cylinders of aconventional reciprocating engine (not shown).

Fuel-mixing apparatus 11 includes an air horn 14 through which air isdrawn from the atmosphere into a mixing chamber 15. A conventional aircleaner 16 is provided at the inlet to air horn 14 to filter the airdrawn therethrough.

Mixing apparatus 11 also includes a fuel nozzle 18 for injecting fuelinto mixing chamber 15 wherein a turbulence generator 19 is provided formixing fuel and air drawn thereinto. Turbulence generator 19 maycomprise any device suitable for mixing fuel and air. It may, forexample, comprise fixed vanes at the exit of mixing chamber 15 or it maybe a moving element. A throttle valve 20 is provided at the base ofmixing apparatus 11 so as to control the rate at which fuel mixtureenters manifold 12. Throttle valve 20 is a butterfly valve which rotatesabout an offcenter pivot axis 21 such that the partial vacuum normallyexisting within manifold- 12 tends to maintain it in a closed position.I

Reference numeral 25 designates a fuel-metering valve which controls thefuel flow to fuel nozzle 18. Metering valve 25 is connected to besupplied with fuel from a fuel source (not shown) by means of a fuelline 26, a fuel pump 27, a shut off valve 28 and fuel lines 29. Fuelvalve 25 is connected to fuel nozzle 18 by means of a fuel line 22. Fuelvalve 25 may be of any suitable type wherein fuel flow is controlled inresponse to a differential pressure control signal supplied thereto.Many such devices are known in the prior. art. One such suitable deviceis shown in the applicants copending application Ser.

No. 721,994, filed Apr. 17, 1968, and assigned to the assignee of thepresent application. Additional devices, such as a vapor separator maybe included in fuel lines 29 as desired. However, such devices are wellknown and will not be shown to simplify the drawing.

.Reference numeral 30 generally designates fluidic control apparatus forcontrolling fuel valve 25. Control apparatus 30 includes an air flowvelocity sensor 31, an air temperature sensor 32, an air pressure sensor33, an engine demand sensor 34, an engine temperature sensor and afluidic computer circuit 36.

Computer circuit 36 comprises a plurality of fluid amplifiers designatedby reference numerals 40 47. Amplifiers 40, 41 and 43-47 areproportional devices. Amplifier 42 may be either proportional orbistable. Each of these amplifiers includes a power nozzle a, a firstpair of opposing control ports b andc, a first outlet passage d and asecond outlet'passage e. in addi ion, amplifiers 40, 41, 43, 44 and 47each include .a second pair of opposing control ports f" and g".Reference hereinafter to a particular element of a fluid amplifier willbe made by amplifier identification number and reference character ofthe particular element. For example, control port b" of amplifier 40will be indicated by control port 40b.

Reference numeral 50 designates to a source of filtered air which isconnected to supply air to a conduit 51 through a valve 52. Powernozzles 40a-44a and 47a are connected to conduit 51 by means of conduits53-58.

The velocity sensor 31 comprises a total pressure probe and a staticpressure probe 61 in communication with the passage through air horn 14.Total pressure probe 60 is connected to control port 40g by means ofconduits 62 and 63. Static pressure probe 61 is connected to controlport 40f by means of conduit 64. Conduits 63 and 64 are connected toconduit 51 through conduit 53 and orifices 65 and 66.

Air temperature sensor 32 comprises a capillary passage located withinair born 14. One end of capillary passage 70 is connected to conduit 51through conduits 56, 57, 58 and 71. The other end of capillary passage70 is connected to control port 41 f through a conduit 72. Control port41g is connected toconduit 58 through an orifice 73 which also comprisesa portion of air temperature sensor 32.

Air pressure sensor 33 includes total pressure probe 60. Total pressureprobe 60 is connected to control port 41b through conduits 62 and 74.

Engine demand sensor 34 comprises a pressure port 75 in communicationwith the interior of manifold 12. Pressure port 75 is connected tocontrol port 42c through a conduit 76 and an orifice 77. Control port42b is vented to the atmosphere through an orifice 78. Outlet passage42d is connected to control port 41c through a conduit 79. Outletpassage 42a is vented to the atmosphere.

Engine temperature sensor 35 comprises a capillary passage 80 in thermalcommunication with the engine (not shown). One end of capillary passage80 is connected to conduit 51 through conduit 53. The other end ofcapillary passage 80 is connected to control port 40c through a conduit81. Control port 40b is connected to conduit 51 through an orifice 82which also comprises a portion of engine temperature sensor 35;

Outlet passages 40d and 40e are connected to control ports 44g and 44fthrough conduits 85- and 86. Control ports 44g and 44f comprise a firstinput to a fluidic multiplier circuit which includes amplifiers 44, 45and 46 and interconnecting conduits 91-96. Conduits 95 and 96 comprise asecond input to multiplier circuit 90. Conduits 95 and 96 are connectedto amplifier 41 through amplifier 43. Specifically, outlet passages 41dand 41e are connected to control ports 43g and 43f through conduits 100and 101. Outlet passages 43d and 43e are connected to conduits 96 and 95through conduits 102 and 103. Amplifier 43 is provided with negativefeedback paths through variable orifices 104 and 105.

Multiplier circuit 90 may be of any suitable type capable of producingan output signal .which is the product of input signals suppliedthereto. However, the circuit shown in the figure is the subject of U.S.Pat. application Ser. No. 659,964 filed Aug. 11, 1967 in the name ofCharles W. Rainer, now U.S. Pat. No. 3,499,440 and assigned to theassignee of the present application. Fluidic multiplier circuit 90 isfully described in the above-identified application. No additionaldescription is necessary.

Outlet passages 45e and 46d comprise-the output of multiplier circuit90. Outlet passages 45e and-46d are connected to control ports 47g and47f through conduits and 111. Outlet passages 47d and 47e are connectedto the control input of fuel valve 25 through conduits 112 and 113.Amplifier 47 is provided with negative feedback paths through variableorifices 114 and 115.

In normal operation of the engine with which fuel supply apparatus 10 isassociated, the action of the pistons and valves within the enginecauses a partial vacuum in intake manifold 12. The reduced pressurewithin manifold 12 functions to draw fuel mixture from mixing chamber 15at a rate depending on the position of throttle valve 20 and thepressure differential thereacross. The removal of fuel mixture frommixing chamber 15, in turn, results in air flow through air horn 14. Inorder to maintain the proper fuel to air mass ratio in mixing chamber15, fuel flow into chamber 15 is controlled in' response to mass airflow thereinto. The applicants fluidic fuel control system functions tocontrol fuel flow into mixing chamber 15 in responseto mass air flowthereinto as follows. As a prerequisite to operation of the applicantsfuel control system, filtered air under pressure must be provided topower the fluid amplifiers and certain of the sensors. In addition, fuelunder pressure must be supplied to fuel-metering valve 25. Air underpressure may be supplied by' 'means of a compressor operating as anengine accessory Lilcewise, fuel under pressure may be provided by meansof a fuelpump operating as an engine accessory.

During engine start up, engine power is not available. However, sincethe air and fuel pressure required to power fluidic control apparatus 30and supply fuel under-pressure to fuel valve 25 is not substantial,cranking the. engine during the starting process will provide sufficientair and fuel pressure to start the engine. In addition, the fuel valve25may be constructed such that in the absence of any control signals, itwill allow a predetermined flow of fuel therethrough sufficient to startthe engine. A temperature controlled mechanical choke may be providedfor limiting the air flow through air horn 14 so as to enrich the fuelmixture and to provide for easy engine starting.

With source 50 in operation and valve 52 open, air under pressure issupplied directly to power nozzles 40a-44a and 47a, thereby causingfluid streams to issue therefrom. In addition, as described inpreviously mentioned application Ser. No. 659,964, air in varyingamounts is supplied to power nozzles 45a and 46a from outlet passages44d and 44e. The operation of amplifiers 40-47 is identical. Therefore,only the operation of amplifier 40 will be discussed in detail. In theabsence of pressure differential signals supplied to the control portsof amplifier 40, the fluid stream issuing from power nozzle 404 will besubstantially equally divided between outlet passages 40d and 40e.Accordingly, in the absence of pressure differential input signals toamplifier 40, no pressure differential output signals will be producedthereby. However, if a pressure differential input signal is supplied toeither or both pairs of opposing control ports, a pressure differentialoutput signal will generally be produced between outlet passages 40d and40s. If a pressure differential signal is supplied to the first pair ofopposing control ports such that the pressure at control port 40 b isgreater than the pressure at control port 40c, the pressure produced inoutlet passage 40d will be greater than the pressure produced in outletpassage 40c. Similarly if a pressure differential signal is supplied tothe second pair of opposing control ports such that the pressure atcontrol port 40f is greater than the pressure at control port 40g, thepressure produced in outlet passage 40d will be greater than thepressure produced in outlet passage 40c.

Air velocity sensor 31 operatesto produce a pressure differential signalindicative of the velocity of air flow through air born 14 as follows.Air under pressure is supplied to total pres sure probe 60 throughconduit 53, orifice 65, conduit 63 and conduit 62. Air under pressure isalso supplied to static pressure probe 61 through conduit 53, orifice 66and conduit 64. Thus, air flows out of probes 60 and 61 into air horn14.

The rate at which air flows from probes 60 and 61 is dependent on the.pressures present at the respective probes. The pressure at totalpressure probe 60 is independent of air flow velocity through air horn14. The pressure at static pressure probe 61 varies inversely with airflow velocity through air born 14. Thus, the differential in flow ratesfrom probes 60 and 61, and consequentlythe pressures produced inconduits 63 and 64, varies with flow velocity through air horn 14.Specifically, as the flow velocity through air horn 14 increases, thepressure in conduit 63 increases with respect to the pressure in conduit64. Since the cross-sectional area of air born 14 is fixed, the pressuredifferential between conduits 63 and 64 is also indicative of thevolumetric rate of air flow into mixing chamber 15.

The pressure signals in conduits 63 and 64 are supplied to one pair ofcontrol ports of amplifier 40. Amplifier 40 is also supplied with apressure differential signal indicative of engine temperature fromengine temperature sensor 35.

In order to understand the operation of engine temperature sensor 35 andair temperature sensor 32, it is necessary to know the effects oftemperature on air flow through a simple orifice and through a capillarypassage. Air flow through a simple orifice is substantially independentof temperature over the range of temperatures to which a fuel controlsystem for an engine would normally be exposed. However, over the samerange of temperatures, impedance to air flow through a capillary passageis directly dependent upon the viscosity of the air which, in turn, isdirectly dependent upon the air temperature. Accordingly, as thetemperature of the air flowing through a capillary passage increases,pressure drop across the passage increases and air flow throughthepassage decreases. These characteristics of air flow through an orificeand a capillary passage are utilized in the applicants fuel controlsystem.

Control port 40c is supplied with a fluid pressure signal from conduit51 through conduit 53, capillary passage 80 and conduit 81. Capillarypassage 80 is in thermal communication with the engine (not shown). Heatis transferred from the engine to the air within capillary passage 80such that the temperature of the air there within approximates thetemperature of the engine. Thus, as the temperature of the engineincreases, the pressure drop across capillary passage 80 increases andthe pressure signal supplied to control port 400 decreases.

A pressure signal is also supplied to control port 40b, which opposescontrol port 40c, from conduit 51 through orifice 82. Since theimpedance produced by orifice 82 to air flow therethrough issubstantially of temperature, the pressure signal supplied to controlport 40c varies primarily only with changes in pressure supplied theretofrom conduit 51. The pressure supplied to capillary passage 80 fromconduit 51 vaties in the same manner as the pressure supplied to orifice82. Accordingly, the pressure differential signals supplied to controlports 40b and 40c is indicative of only the temperature of the engine.Further, as the temperature of the engine increases, the pressure signalsupplied to control 400 decreases with respect to the pressure atcontrol 40b. Capillary passage 80 and orifice 82 are sized such that fora predetermined normal engine temperature, the pressure signals suppliedto control ports 40b and 40c are substantially equal.

Amplifier 40 functions to sum the pressure signals supplied to controlports 40 b, 40c, 40f and 403. From the previous discussion of amplifier40, it can be seen that as the volumetric rate of air flow into mixingchamber 15 increases, the pressure signal produced in outlet passage 40cincreases relative to the pressure signal produced in outlet passage40d. As the engine temperature increases, the pressure signal producedin outlet passage 40:: decreases relative to the pressure signalproduced in outlet passage 40d.

The pressure signals produced in outlet passages 40d and 40e aretransmitted to control ports 44g and 44f through conduits and 86. Asindicated hereinbefore, control ports 44g and 44f comprise a first inputto fluidic' multiplier circuit 90. Conduits and 96 comprise a secondinput to fluidic multiplier circuit 90. Conduits 95 and 96 are suppliedwith pressure signals from amplifier 43 as will now be described.

A pressure differential signal indicative of the temperature of the airentering mixing chamber 15 is supplied to control ports 41f and 413 fromair temperature sensor 32 as follows. Air temperature sensor 32comprises capillary pasage 70 which is located within air born 14.Control port 41f is supplied with a pressure signal from conduit 51through conduits 56, 57, 58 and 71, capillary passage 70 and conduit 72.A pressure signal is also supplied to control port 413 from conduit 51through conduits 56, 57 and 58 and orifice 73. Capillary passage 70operates inthe same manner as capillary passage 80 to decrease thepressure at control port 41f as the temperature of the air entering themixing chamber 15 increases. The pressure drop across orifice 73 issubstantially independent of temperature. Therefore, as the temperatureof the air entering mixing chamber 15 increases, the pressure at controlport 41 f decreases with respect to the pressure at control port 413.Since the operation of capillary passage 70 is identical to theoperation of capillary passage 80, no further description will beprovided.

Control port 41b is supplied with a pressure signal indicative of thepressure of air entering the mixing chamber 15. This signal is suppliedby conduit 62 which comprises a portion of air pressure sensor 33.Control port 41c, which opposes control port 41b, receives a pressuresignal indicative of engine and/or loading from amplifier 42 as follows.

As previously pointed out, operation of the engine with which intakemanifold 12 is associated results in a partial vacuum within themanifold. For steady state operation the pressure within manifold 12remains constant at some value dependent on the operating conditions ofthe engine. However, if an increase load is placed on the engine, theengine will decelerate. Slowing down of engine operation results in adecrease in the partial vacuum within manifold 12 or an increase inpressure therein. Similarly, if it is desired to accelerate the engine,throttle valve 20 is opened. Opening of throttle valve 20 results in adecrease in the partial vacuum within manifold12 or an increase inpressure therein. Conversely, either a decrease in the load on theengine or closing of throttle valve 20 results in a decrease in pressurewithin manifold 12. Accordingly, any change in the setting of throttlevalve 20 or in the loading condition of the engine (hereinafter referredto as engine demand) results in a change in pressure within manifold 12.Changes in engine demand are reflected as pressure changes at pressureport 75.

For improved transient engine operation, it has been found advantageousto increase the fuel to air ratio when engine acceleration is desired oran increased load is placed on the engine. This is accomplished bytransmitting the pressure signal from pressure port 75 to control port420 through conduit 76 and orifice 77. Control port 42b, which opposescontrol port 42c is vented to the atmosphere through orifice 78. Thesignal produced at outlet passage 42d is transmitted to control port 410through conduit 79. Orifices 77 and 78 are sized such that for normalengine demand conditions and normal pressure of the air entering mixingchamber 15, equal pressures are supplied to control ports 41b and 41c.

Amplifier 41 functions to sum the air temperature, air pressure andengine demand signals and produce a pressure differential output signalbetween outlet passages 41d and 41a indicative of this summation.Specifically, the pressure produced in outlet passage 41c increases withrespect to the pressure produced in outlet passage 41d if the airtemperature increases, the air pressure decreases, and/or engine demanddecreases. The output signal of amplifier 41 is transmitted to controlports 43f and 43g through conduits 101 and 100. Control ports 43b and430 are provided with negative feedback signals through variableorifices 105 and 104. Variable orifices 105 and 104 provide for varyingthe gain of amplifier 43. The signal produced by amplifier 43 istransmitted through conduits 103 and 102 to conduits 95 and 96 whichcomprise the second input to multiplier circuit 90. Variable orifices105 and 104 thus provide for varying the relative magnitudes of thesignals supplied to the first and second inputs of multiplier circuit90.

Fluidic multiplier circuit 90 produces a pressure differential outputsignal indicative of the product of the signals supplied to the firstand second inputs thereof. The output signal of multiplier circuit 90 isproduced between outlet passages 45c and 46d. The operation ofmultiplier circuit 90 is fully described in patent application Ser. No.659,964. Reference 1 may be made to that application for a completeoperational description.

Since the signal supplied to the first input of multiplier circuit 90 isa function of the volumetric rate of air flow into mixing chamber 15 andthe signal supplied to the second input is a function of the temperatureof the air entering mixing chamber 15, it can be seen that the outputsignal of the multiplier circuit is a function of the product ofvolumetric flow rate and temperature of the air entering the mixingchamber. The output signal of fluidic multiplier circuit 90 can thusprovide a much closer indication of mass rate of air flow into mixingchamber 15 than can be provided by prior art systems.

' paths provide means for varying the gain-of amplifier 47. Theoutput'signal from amplifier 47 can thus be'tailored to the signalrequirements of fuel valve 25. The output signal of amplifier 47comprises the output signal of multiplier circuit 90 modified by thegain of amplifier 47. The output signal of amplifier 47 thus alsoprovides an indication of the mass air flow into mixing chamber 15.Since fuel flow into mixing chamber 15 from fuel valve 25 is controlledby this signal, it is apparent that the applicants present fuel controlsystem provides much closer control over the mass fuel to air ratio inmixing chamber 15 than can be provided by prior art systems.

lclaim:

1. In combination with fuel mixing apparatus including a mixing chamberhaving an air intake passage and a fuel nozzle for introducing air andfuel thereinto, the improvement which comprises:

air velocity sensing means operable to produce a fluid signal indicativeof air flow velocity through the air intake passage;

air temperature sensing means operable to produce a fluid signalindicative of air temperature in the air intake passage;

a fluidic multiplier circuit having first, a second, and thirdproportional fluid amplifiers each comprising a power nozzle for issuinga fluid stream, a pair of outlet passages for receiving portions of thefluid stream, and a plurality of control ports for directing the fluidstream toward the outlet passages, said proportional fluid amplifiersconnected so that the outlet passages of said first proportional fluidamplifier supply fluid to the power nozzles of said second and thirdproportional fluid amplifiers, said fluidic multiplier circuit furtherhaving first and second inputs connected to the control ports of theproportional fluid amplifiers and an output connected to outlet passagesof said second and third proportional fluid amplifiers, said fluidicmultiplier circuit operable to produce an output signal indicative ofthe product of the signals supplied to the first and second inputsthereof;

means connecting said air velocity sensing means to the first input ofsaid fluidic multiplier circuit;

means connecting said air temperature sensing means to the second inputof said fluidic multiplier circuit;

fuel control means operable to control fuel flow to the fuel nozzle ofsaid fuel mixing apparatus in response to an input signal; and

means connecting the output of said fluidic multiplier circuit to saidfuel control means. I

2. The apparatus of claim 1 further including air pressuresensing meansoperable to produce a fluid signal indicative of air pressure in the airintake passage and means connecting said air pressure sensing means tothe second input of said fluidic multiplier circuit. i

3. The apparatus of claim 1 in combination with an internal combustionengine and further including demand-sensing means operable to produce afluid signal indicative of engine acceleration and loading and meansconnecting said demandsensing means to an input of said fluidicmultiplier circuit.

4. The apparatus of claim 3 further including engine temperature sensingmeans operable to produce a fluid signal indicative of enginetemperature and means connecting said engine temperature-sensing meansto an input of said fluidic multiplier circuit.

5. The apparatus of claim 4 wherein said means connecting said enginetemperature-sensing means to an input of said fluidic multiplier circuitcomprises means for summing the fluid signal indicative of enginetemperature and the fluid signal indicative of air flow velocity throughthe air intake passage.

6. In combination with fuel-mixing apparatus of the type wherein signalsindicative of a plurality of parameters of air entering a mixing chamberare combined to produce a signal indicative of air mass flow thereintoand wherein fuel flow into the mixing region is controlled in responseto the air mass flow signal, the improvement which comprises:

air velocity sensing means operable to produce a first fluid signalindicative of the volumetric rate of flow of air into the mixingchamber;

air temperature sensing means operable to produce a second fluid signalindicative of the temperature of air entering the mixing chamber; and

fluidic multiplier means including a plurality of proportional fluidamplifiers each comprising a power nozzle for issuing a fluid stream, apair of outlet passages for receiving portions of the fluid stream, andcontrol port means for irecting the fluid stream toward the outletpassages, said air velocity sensing means and said air temperaturesensing means connected to said control port means so that a third fluidsignal indicative of a product of the first and second fluid signals isproduced, said third fluid signal for controlling fuel flow into themixing chamber.

7. The apparatus of claim 6 further including air pressure sensing meansoperable to produce a fourth fluid signal indicative of the pressure ofair entering the mixing chamber and means connecting said air pressuresensing means to said fluidic multiplier means, said third fluid signalfurther being a function of the pressure of air entering the mixingchamber.

8. The apparatus of claim 7 in combination with an internal combustionengine and further including demand sensing means operable to produce afifth fluid signal indicative of engine acceleration and loading andmeans connecting said demand-sensing means to said fluidic multipliermeans, said third fluid signal further being a function of engineacceleration and loading.

9. The apparatus of claim 8 further including engine temperature-sensingmeans operable to produce a sixth fluid signal indicative of enginetemperature and means connecting said engine temperature-sensing meansto said fluidic multiplier means, said third fluid signal further beinga function of engine acceleration and loading.

ll). The apparatus of claim 9 wherein:

said air velocity sensing means includes a total pressure probe and astatic pressure probe operable to produce signals indicative of thetotal pressure and static pressure of air entering the mixing region;and

said air temperature sensing means comprises a capillary passage locatedin the air entering the mixing chamber

